Recent content by apchar

Time is natures way of keeping everything from happening at once. ;->

I'd like to make a strong (~0.5 T) solenoidal field with a permanent magnet for a Faraday rotation experiment. If I take an ordinary cylindrical permanent magnet (with an axial field) and drill a hole down the center of it. What's the field deep inside at the center of the hole? Some of the flux...

But the dimensions of an antenna have to be comparable to the wavelength to be effective (D ~ lambda), making the point at which the far field begins a wavelength or two away. Is the same not true for lasers? What about scattered laser light?

The intensity (W/m^2) of an electromagnetic wave from an ordinary antenna decreases with the square of the distance from the emitter (in the far field.) Is the same true for a laser beam?

That's too macroscopic. It treats the inductor as a black box. I can build all manner of 1 port circuits that resist a change in the current flow but that doesn't make them inductors. I'm looking for a definition based on the physics.

My old freshman physics text defined inductance as flux/turns, which applies only to solenoids. This seems like a pretty weak definition since any length of wire in any geometry has some inductance. There has to be a more general definition. My first guess was that L could be calculated from...

Krypton is a gas. I was thinking of something solid. I know Krypton is used in some bulbs. Is that the isotope commonly used? I could affix a small Krypton bulb to my big Xenon bulb.

We're building a very high power xenon flashlamp with electrodes so far apart that some kind of pre-ionization is necessary to start the discharge. I dump 10,000 volts across the electrodes so I just need a few loose electrons to get the ball rolling. I've been using a Tesla coil to get a...

The Biot-Savart law for calculating magnetic fields due to a current is presented in my freshman physics book as a general way of getting B from I. But there's no time delay implied by the integral. Can I just manually throw the time delay into the integral? For instance, to numerically...

I'm working on a lightning bolt experiment at U of Washington to see how carbon composite materials hold up when hit by lightning. We have as much as a 40 kV 80 kA 50 us arc across a <1cm gap from a copper/tungsten electrode to a plate of carbon composite connected to ground. I know this must...